An electrostatic chuck is used for attracting and holding a semiconductor substrate in various apparatuses such as an ion implantation apparatus, an ion doping apparatus, and a plasma immersion in a semiconductor manufacturing process, an exposing apparatus using an electron beam or an extreme ultraviolet (EUV) lithography, or a wafer inspection apparatus for silicon wafers or the like. In addition, in a field of manufacturing liquid crystal displays, the electrostatic chuck is used for attracting and holding an insulating substrate in a substrate combining apparatus, which is used for filling liquid crystal between glass substrates, or in an ion doping apparatus.
The electrostatic chuck usually attracts a substrate via an upper insulating layer made of a high electric insulating material such as a polyimide film or a ceramic material. In addition, the electrostatic chuck is used inside a vacuum chamber or in the environment with very low humidity. Therefore, the electrostatic chuck itself is apt to be charged easily. Therefore, there is a problem that charged particles such as ions and electrons that are used for processing of the substrate may be attracted by the upper insulating layer so as to generate residual charges, which maintains the substrate in the attracted state even after a long period from power-off. In addition, there is also a problem that charged and floating particles around the electrostatic chuck may be attracted.
In order to cancel residual charges of the electrostatic chuck, it is necessary to provide a path for the accumulated charges to flow easily to the earth (ground) or the like, or to supply charges having opposite polarity to the portion where the charges exist. However, in recent years, a structure of the electrostatic chuck is apt to be complicated because of necessities of improving attraction force of the electrostatic chuck or processing substrates of increasing size. For this reason, it is difficult to cancel the residual charges completely by leading the charges to flow to the earth or by supplying charges having the opposite polarity.
Therefore, there is proposed a method, for example, in which a part of the upper insulating layer on the substrate side is cut off (step section is provided) corresponding to the part of the electrode layer where no electrode exists so that the upper insulating layer does not contact directly with the substrate in the part where no electrode exists (see FIG. 1(c) of Patent Literature 1). In the upper insulating layer corresponding to the part where no electrode exists, there is formed a dielectric polarization along the transverse direction connecting the end of the electrode existing nearby and the substrate to be attracted. The charges accumulated in this direction are hardly canceled by electric control after voltage application is stopped. Therefore, the above-mentioned proposal relates to a method of canceling charges that are hardly canceled by electric control, by cutting off the upper insulating layer corresponding to the part where no electrode exists.
However, as described above, in recent years, an electrode having a complicated shape such as a comb-shaped electrode is studied for improving the attraction force, and hence it is actually difficult to adopt the above-mentioned method for such electrode. In addition, even if the above-mentioned method can be adopted, it is necessary to supply appropriate and proper amount of charges having the opposite polarity to the part where residual charges exist, in order to cancel completely the charges accumulated once in the electrostatic chuck by electric control or the like. The control or the like is very difficult.